Urethane polymers have in the past been modified to modulate their functionality by endcapping some or all of the isocyanate groups with a variety of organosilanes to yield silane end-capped urethane polymers containing minimal or no isocyanate groups.
The production of isocyanato terminated polyurethane polymers by the reaction of polyurethane prepolymer with an organosilane having one or more hydrolyzable alkoxysilane groups is known in the art. The polyurethane prepolymer used must have terminal active hydrogens. These terminal hydrogens can be present in groups such as hydroxyl groups, mercapto groups, or primary or secondary amino groups. These active hydrogen atoms are reacted with an isocyanate group present in the organosilane compound. The hydroxyl compounds are used in molar excess with respect to the polyisocyanate so that the resulting reagents have hydroxyl terminals.
The endcapping procedure used when making these polymers involves a sequential reaction mechanism. In other words, the endcapping silanes must be added when the NCO % is at or very close to zero, in order to obtain sufficient yields of silane-terminated polyurethane prepolymers (SPUR) having the desired viscosity and properties. For example, a conventional process used to make a silane-terminated polyurethane reacts polymer diols with isocyanate first and then adds functional silane to cap the ends of the terminates once the NCO % is close or at zero. If the silane end-cappers are added prematurely, i.e. before the NCO % is close or at zero, the properties of the polymer resulting varies greatly. In fact, it is a great challenge for manufactures to determine and then cap the SPUR prepolymers accurately in order to obtain consistent properties from batch to batch.
In view of the foregoing, what is needed is a process for producing moisture-curable silylated resin compositions wherein the addition of silane endcappers can be done at anytime during the reaction mechanism with little or no variation in the properties of the resulting silylated resin compositions. This process would decrease the variation of SPUR prepolymers form batch to batch. In other words, the resulting prepolymer resin compositions would have the same or similar viscosity and other properties regardless of the order in which the silane endcappers were added to the reaction. The process described herein and the products produced from the claimed processes overcome the problems of the prior-art.